Air-Conditioning System Provided With a Heat Pump

ABSTRACT

The invention relates to an air-conditioning system ( 1 ), in particular a motor vehicle air-conditioning system ( 1 ) comprising a coolant circuit ( 2 ) provided with a coolant compressor ( 3 ) and a gas cooler ( 4 ), an internal heat exchanger ( 5 ), an expansion unit ( 7 ) and an evaporator ( 8 ) Said invention is characterised in that a device for turning back the coolant flow direction is provided for the heal pump operation and means for switching off the internal heat exchanger ( 5 ) when the flow direction is reversed is also provided.

The invention relates to an air conditioning system, in particular for amotor vehicle, according to the preamble of claim 1.

An air conditioning system of such type is known from DE 36 35 353, inwhich the air conditioning system can also be operated as a heat pump,the energy which needs to be fed to the refrigeration circuitoriginating from the energy losses of the motor vehicle, that is to sayfrom the hot coolant heat energy which is otherwise discharged, withoutbeing utilized, to atmosphere, via the radiator of the motor vehicle.For this purpose, a heat exchanger is provided which, during heatingoperation of the air conditioning system, serves as an evaporator forthe refrigerant, the energy for evaporation of the refrigerant beingtaken from the hot engine refrigerant, so that the coolant is evaporatedthrough utilization of the coolant energy.

An air conditioning system of such type can however be improved.

It is an object of the invention to provide an improved air conditioningsystem.

This object is achieved by means of an air conditioning system havingthe features of claim 1. Advantageous embodiments are the subject matterof the subclaims.

According to the invention, an air conditioning system, in particular amotor vehicle air conditioning system, having a circuit is provided, inwhich circuit are arranged a refrigerant compressor, a gas cooler, aninner heat exchanger, an expansion element and an evaporator, a devicefor reversing the flow direction of the refrigerant being provided forheat pump operation, and means being provided which deactivate the innerheat exchanger while the flow direction is reversed. In normaloperation, that is to say in AC operation, the refrigerant flows fromthe gas cooler (first heat exchanger) to the expansion element, and fromthe evaporator (second heat exchanger) to the refrigerant compressor,are thermally coupled by means of the inner heat exchanger. In heat pumpoperation, however, the inner heat exchanger is bypassed, so that thereis no thermal coupling between the refrigerant flows. The entirearrangement makes possible a simply constituted heat pump withoutadditional components in the refrigerant circuit.

The means which deactivate the inner heat exchanger while the flowdirection is reversed preferably comprise two non-return valves whichare arranged in corresponding lines provided in parallel with the innerheat exchanger. Here, the non-return valves can also be provided on orin the inner heat exchanger.

The device for reversing the flow direction is preferably formed bymeans of a suitable means of switching to a cross-over circuit of theback pressure and high pressure connections on or in the refrigerantcompressor.

An expansion element having two antiparallel bypasses is preferablyprovided in the circuit. This is preferably an orifice expansion elementhaving two flow-direction-dependent antiparallel bypasses.

The evaporator assumes the heating function during heat pump operation.

CO₂ is preferably used as the refrigerant. Other refrigerants arehowever also possible.

A compressor regulator valve and a device for switching the refrigerantflow direction are preferably electrically controlled.

An adjustable stroke volume of the refrigerant compressor forcontrolling the refrigeration power, (AC operation) and the heatingpower of the heat pump is particularly advantageous.

The invention is described in de tail in the following on the basis ofan exemplary embodiment and with reference to the drawing, in which:

FIG. 1 shows a schematic illustration of an air conditioning systemaccording to the invention in AC operation, only those componentsrelevant to this operating state being illustrated, and

FIG. 2 shows a schematic illustration of the air conditioning systemfrom FIG. 1 in heat pump operation.

An air conditioning system 1 has a circuit 2 having a refrigerantcompressor 3, a first heat exchanger 4 which is connected downstream ofsaid refrigerant -compressor 3 and serves as a gas cooler in ACoperation, an inner heat exchanger 5, an expansion element 7 having twoantiparallel bypasses, and a second heat exchanger 8 which serves as anevaporator in AC operation.

Refrigerant flows clockwise through the circuit 2 in AC operation, asillustrated in FIG. 1. In the inner heat exchanger 5, heat is exchangedhere between refrigerant coming from the first heat exchanger 4 andrefrigerant coming from the second heat exchanger 8.

If there is a change in mode to heat pump operation by means of across-over circuit of the back pressure and high pressure connections onor in the refrigerant compressor 3, the inner heat exchanger 4 isdeactivated on account of non-return valves 9 arranged in correspondinglines. On account of the reversed throughflow direction, as illustratedin FIG. 2, flows passes through the circuit 2 counter-clockwise. Here,the first heat exchanger 4 assumes the function of an evaporator and thesecond heat exchanger 8 acts as an additional heater.

The expansion element 7 embodied by means of two antiparallel bypassescan be used without external control measures in both operating modes,that is to say in AC operation and in heat pump operation.

LIST OF REFERENCE DESIGNATIONS

-   1 Air conditioning system-   2 Circuit-   3 Refrigerant compressor-   4 First heat exchanger-   5 Inner heat exchanger-   7 Expansion element-   8 Second heat exchanger-   0 Non-return valve

10 Line

1. An air conditioning system, in particular a motor vehicle airconditioning system, having a circuit through which refrigerant flowsand in which are arranged a refrigerant compressor and a first heatexchanger, an inner heat exchanger, an expansion element and a secondheat exchanger, the first heat exchanger serving as a gas cooler in ACoperation and the second heat exchanger serving as an evaporator in ACoperation, wherein a device for reversing the flow direction of therefrigerant is provided for heat pump operation, and means are providedwhich deactivate the inner heat exchanger while the flow direction isreversed.
 2. The air conditioning system as claimed in claim 1, whereinthe means which deactivate the inner heat exchanger while the flowdirection is reversed preferably comprise two non-return valves.
 3. Theair conditioning system as claimed in claim 1, wherein the device forreversing the flow direction of the refrigerant comprises a cross-overcircuit of the back pressure and high pressure connections on or in therefrigerant compressor.
 4. The air conditioning system as claimed inclaim 2, wherein the non-return valves are provided on or in the innerheat exchanger.
 5. The air conditioning system as claimed in claim 1,wherein the refrigerant compressor can be operated in two directions ora correspondingly acting configuration of lines and valves is provided.6. The air conditioning system as claimed in claim 1, wherein anexpansion element having antiparallel bypasses is provided in thecircuit.
 7. The air conditioning system as claimed in claim 1, whereinthe heat exchanger which serves as an evaporator in AC operationfunctions as a heater in heat pump operation.
 8. The air conditioningsystem as claimed in claim 1, wherein CO₂ is used as the refrigerant. 9.The air conditioning system as claimed in claim 1, wherein a compressorregulator valve and a device for switching the refrigerant flowdirection are electrically controlled.
 10. The air conditioning systemas claimed in claim 1, wherein the stroke volume of the refrigerantcompressor is adjustable.
 11. A method for operating an air conditioningsystem as claimed in claim 1, the refrigerant flowing through thecircuit counter to the normal flow direction, and the inner heatexchanger being bypassed, during heat pump operation.